<i>double</i> v = <b>double.infinity</b>				<em>// 正无穷，无限大 => Infinity</em>
<i>double</i> v = <b>double.negativeInfinity</b>		<em>// 负无穷，无限小 => -Infinity</em>
<i>double</i> v = <b>double.nan</b>					<em>// 数字是 double 非数字值 => NaN</em>
<i>double</i> v = <b>double.minPositive</b>			<em>//  => 5e-324</em>
<i>double</i> v = <b>double.maxFinite</b>			<em>//  => 1.7976931348623157e+308</em>